Evolutionary study of maize dwarf mosaic virus using nearly complete genome sequences acquired by next-generation sequencing.

Next-generation sequencing is a robust approach to sequence plant virus genomes in a very short amount of time compared to traditional sequencing methods. Maize dwarf mosaic virus (MDMV) is one of the most important plant viruses worldwide and a significant threat to maize production. In this study, we sequenced 19 MDMV isolates (10 from Johnsongrass and 9 from maize) collected in Oklahoma and Missouri during 2017-2019 using Illumina sequencing and determined the genetic diversity. Sequence reads were assembled and 19 nearly complete genome sequences of MDMV isolates were obtained. Phylogenetic analysis based on complete genomes nucleotide and amino acid sequences revealed two main clusters and a close evolutionary relationship among 19 MDMV isolates. Statistical analysis of individual genes for site-specific selection revealed that all genes are under negative selection. The fixation index (FST) analysis of the MDMV isolates revealed no gene flow between the two main phylogenetic clusters, which emphasizes the divergence of MDMV isolates from the USA. Among the USA MDMV isolates, the mean genetic distance (d) and nucleotide diversity ((π) were highest in the P1 gene coding region. This is the first detailed study on the evolutionary relationship of MDMV isolates based on the nearly complete genome analysis from maize and Johnsongrass.